[Numpy-discussion] Behavior of nan{max, min} and nanarg{max, min} for all-nan slices.

Benjamin Root ben.root at ou.edu
Thu Oct 3 09:10:56 EDT 2013


On Thu, Oct 3, 2013 at 6:06 AM, Daniele Nicolodi <daniele at grinta.net> wrote:

> Hello,
>
> sorry, I don't know where exactly jump in in the thread, it is getting
> quite long and articulated...
>
> On 02/10/2013 21:19, Charles R Harris wrote:
> > The main problem I had was deciding what arg{max, min} should return as
> > the return value is an integer. I like your suggestion of returning 0.
>
> What about returning -1? It is still an integer (on my numpy version the
> return value is a signed integer), it still has the property that
> a[np.argmin(a)] == nan for a of only nans, but it is easily identifiable
> as an anomalous return value if needed.
>
>
This actually makes a lot of sense. We would never return -1 for any other
reason. And if it is used for indexing anywhere else, that's (mostly) ok. A
problem might occur if the indexes gathered from this function are then
used to define slices. But I can't really convince myself that it would be
all that terrible in that case, too. Documentation will be paramount here.

Ben Root
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